If I were single and had OTA available, I would probably do exactly what you're doing. It's at least worth trying for a month or so. I think the only thing that I would miss are some sporting events that are only broadcast on regional sports networks (like Fox Sports West here in California).
Something no one else has mentioned is that you can watch a bunch of cable programming online at hulu.com. I believe there's also a site called surfthechannels.com or something like that. Plus, there's always torrents.
Does D* still let you suspend service? If you did that for a month, then it would be no hassle whatsoever to go back if you decided to keep the service.